This invention relates to techniques for manufacturing circuitry. The invention also relates to methods of testing circuitry.
When manufacturing circuitry, after attaching components to a substrate, such as to a circuit board or flexible material, it is desirable to perform testing. These tests, among other things, are to make sure that circuit connections have been properly made, are sufficiently conductive, and are not cold connections. Such testing is known in the art as xe2x80x9cin-circuitxe2x80x9d testing. It is difficult to perform such testing while power is supplied to the circuitry, such as by an on board cell or battery.
In circuit testing is performed for a wide variety of types of circuitry. Just one example of circuitry for which in circuit testing is performed is in identification circuitry.
As large numbers of objects are moved in inventory, product manufacturing, and merchandising operations, there is a continuous challenge to accurately monitor the location and flow of objects. Additionally, there is a continuing goal to interrogate the location of objects in an inexpensive and streamlined manner. One way of tracking objects is with an electronic identification system.
Some such systems generally include an identification device including circuitry provided with a unique identification code in order to distinguish between a number of different devices. Typically, the identification devices are entirely passive (have no power supply). However, this identification system is only capable of operation over a relatively short range, limited by the size of a magnetic field used to supply power to the devices and to communicate with the devices.
Another type of electronic identification system, and various applications for such systems are described in detail in commonly assigned U.S. patent application Ser. No. 08/705,043, filed Aug. 29, 1996, and incorporated herein by reference. The system includes an active transponder device affixed to an object to be monitored which receives a signal from an interrogator. The device receives the signal, then generates and transmits a responsive signal. Because active devices have their own power sources, they do not need to be in close proximity to an interrogator or reader to receive power via magnetic coupling. Therefore, active transponder devices tend to be more suitable for applications requiring tracking of a tagged device that may not be in close proximity to an interrogator. For example, active transponder devices tend to be more suitable for inventory control or tracking.
Electronic identification systems can also be used for remote payment. For example, when a radio frequency identification device passes an interrogator at a toll booth, the toll booth can determine the identity of the radio frequency identification device, and thus of the owner of the device, and debit an account held by the owner for payment of toll or can receive a credit card number against which the toll can be charged. Similarly, remote payment is possible for a variety of other goods or services.
Testing of battery powered circuitry of this or other types typically requires delaying connection of the battery to the circuit until in circuit testing is completed. Then, another in circuit test must be performed to verify the battery connections.
The invention provides a method of manufacturing and testing an electronic circuit. A plurality of conductive traces are formed on a substrate and a gap is provided in one of the conductive traces. A circuit component is attached to the substrate and coupled to at least one of the conductive traces. A battery is supported on the substrate and coupled the battery to at least one of the conductive traces, wherein a completed circuit would be defined, including the traces, circuit component, and battery, but for the gap. Electrical connections are verified by performing an in circuit test, after the circuit component is attached and the battery is supported. A jumper is employed to electrically close the gap, and complete the circuit, after the electrical connections are verified.
In one aspect of the invention, employing the jumper comprises employing conductive epoxy.
In another aspect of the invention, employing a jumper comprises placing a conductor across the gap and coupling the conductor to traces on either side of the gap with conductive epoxy.
In another aspect of the invention, employing a jumper comprises placing a resistor across the gap and coupling the resistor to traces on either side of the gap with conductive epoxy.
In one aspect of the invention, a jumper is formed by wire bonding; e.g., by ultrasonically bonding a wire loop to traces on either side of the gap.
In one aspect of the invention, the battery is mechanically supported from the substrate by epoxy. In another aspect of the invention, the battery is electrically coupled to at least one of the traces by conductive epoxy.
Another aspect of the invention provides an electronic circuit comprising a substrate, and a plurality of conductive traces on the substrate, with a gap in one of the conductive traces. A circuit component is attached to the substrate and coupled to at least one of the conductive traces. A battery is supported on the substrate and coupled to at least one of the conductive traces, wherein a completed circuit would be defined, including the traces, circuit component, and battery, but for the gap. A jumper electrically closes the gap and completes the circuit. The jumper comprises conductive epoxy.
In one aspect of the invention, the jumper comprises conductive epoxy having a resistance of less than 1000 ohms prior to curing.
In another aspect of the invention, the jumper comprises a conductor across the gap and the conductive epoxy couples the conductor to the conductive traces on either side of the gap.
In another aspect of the invention, the jumper comprises a resistor across the gap and the conductive epoxy couples the resistor to the conductive traces on either side of the gap.
In another aspect of the invention, the size of the gap is approximately 30 thousandths of an inch.
In another aspect of the invention, the circuit component comprises an integrated circuit. In one aspect of the invention, the circuit component comprises an integrated circuit defining a wireless identification device including a receiver, a transponder, a microprocessor, and a memory.